盐度升高对中华绒螯蟹几种非特异性免疫因子的影响

采用逐步增盐法, 结合生物酶学测定, 研究了从淡水升高盐度到 7、14、21、28和35对二秋龄雌、雄中华绒螯蟹血清总蛋白、氧合血蓝蛋白含量及碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)、酚氧化酶(PO)活力的影响。结果显示, 随着盐度的升高, 中华绒螯蟹的血清总蛋白、氧合血蓝蛋白含量逐渐降低; AKP活性先略升高, 而后逐渐降低; 与雄蟹的PO活力逐渐降低相比, 雌蟹的PO活力先降低, 当盐度高于21后维持稳定水平; SOD活性先略降低, 盐度高于21被激活。除SOD外, 雌蟹血清各测定指标均显著高于雄蟹(P<0.05)。研究结果表明, 盐度接近或超过28将显著影响中华绒螯蟹3种免疫酶的活性及总蛋白和氧合血蓝蛋白的含量, 进而影响其免疫防御能力。     

Phenoloxidase and peroxidase activity in the shrimp Litopenaeus schmitti,Pérez‐Farfante and Kensley (1997) exposed to low salinity

Phenoloxidase and peroxidase activity were analysed in haemolymph of juvenile shrimp, Litopenaeus schmitti, exposed to different salinity levels (35%, 18%, 8%) for 48 h. A significant reduction (P<0.05) in total glucose and phenoloxidase activity in animals exposed to lower salinities (18% and 8%) was recorded, while peroxidase activity and total protein concentration did not vary. Histology revealed the occurrence of oedema in gills in shrimp exposed to 8%. The work demonstrates for the first time that in L. schmitti, low salinities can decrease glucose levels in haemolymph and create an immunosuppressive state by reducing phenoloxidase activity.     

The Sydney rock oyster Saccostrea glomerata (Gould 1850) breeding programme: progress and goals

In 1990, NSW Fisheries initiated a mass selection programme in Port Stephens, NSW, with the aim of breeding faster growing Sydney rock oysters Saccostrea glomerata (Gould 1850). After two generations of selection, an average weight for age advantage of 18% (range 14–23% per breeding line) was achieved. This equates to a reduction of 3 months in the time taken to reach market size. Experiments are planned to determine how much of this 3 months advantage is additive to the 6 months advantage this laboratory has already obtained using triploid S. glomerata. A parallel set of S. glomerata breeding lines was established on the Georges River, NSW, to include selection for resistance to the protistan parasite Mikrocytos roughleyi, the causal agent of winter mortality. The programme was disrupted by the outbreak of QX disease Marteilia sydneyi, another protistan parasite, in 1994. In 1997, the breeding programme was reorganized and expanded. New lines were bred from oysters that had survived both QX and winter mortality. After one generation, a small improvement in resistance to QX has been recorded; however, the exposure of further generations to M. sydneyi will be required to confirm an increase in resistance.     

Resistance of Dermo in eastern oysters, Crassostrea virginica (Gmelin), of North Carolina but not Chesapeake Bay Heritage

Growth, intensity of Perkinsus marinus (Levine) infection, and survival of synchronously spawned North Carolina (NC) and Chesapeake Bay‐heritage (CB) oysters, Crassostrea virginica (Gmelin) were evaluated under standard tray culture conditions at several sites in both regions (Wye River, Maryland; Mobjack Bay, Virginia; Pamlico River, NC and Bogue Banks, NC). Infection prevalence reached 100% in oysters held at all high‐ and moderate‐salinity sites, at which time the CB strain ceased to grow. Shortly after growth ceased, CB oysters exhibited mortality that rapidly progressed to 100%. Unlike the CB strain, growth continued in the NC strain despite high P. marinus prevalence. When mortality did occur in the NC strain, at a reduced rate of 37–40%, it was associated with higher intensity of P. marinus than the infection intensity correlated with death of CB oysters. At the low‐salinity site in NC, P. marinus infection persisted at low weighted prevalence throughout the latter portion of the culture period but was not associated with mortality of either strain. These trends in growth and disease resistance for the two strains demonstrate that aquaculture performance is related to the level of disease resistance in oyster strains, salinity of water in growing areas and virulence of P. marinus.     

Evaluation of the progeny of third-generation Sydney rock oyster Saccostrea glomerata (Gould, 1850) breeding lines for resistance to QX disease Marteilia sydneyi and winter mortality Bonamia roughleyi

A breeding program for Sydney rock oysters Saccostrea glomerata (Gould, 1850) has been selecting oysters for resistance to QX disease (Marteilia sydneyi) and winter mortality (Bonamia roughleyi) for three generations at three sites in Georges River, New South Wales, Australia. The experimental sites are located at the upper, middle and lower reaches of oyster growing areas in the estuary. QX disease mainly occurs in the middle and upper reaches and is most severe at the latter. Winter mortality on the other hand occurs mainly at the lower and middle reaches and is most severe at the former. Progeny of third‐generation Sydney rock oyster breeding lines were evaluated for resistance to both QX disease and winter mortality against a non‐selected control. Line 1, selected for QX disease resistance at the upper estuary site, had excellent resistance to one season of exposure to disease, but suffered high mortality during the second season of exposure. However, these oysters had already reached market size of 50 g whole weight, with low mortality at 2 years of age, before the second episode of QX disease. Line 2 showed good improvement in resistance to both diseases, whereas Line 3, was the most resistant to winter mortality. Selection for resistance to QX disease did not appear to confer resistance to winter mortality and the converse also applied.     

Growth trials of Crassostrea gigas and Ostrea edulis in inshore waters of Malta (Central Mediterranean)

To investigate the possibility of establishing oyster culture in Malta, growth trials with C. gigas and O. edulis were undertaken. The oysters were placed in floating cages at depths of 3 and 8 m at Marsaxlokk bay, Mistra bay and Rinella creek. These oysters were sampled at two-month intervals for their growth, meat-shell index and survival. The temperature, salinity, oxygen tension, chlorophyll-a levels and the levels of particulate matter in suspension in the water at the test sites were monitored concurrently. A programme of qualitative and quantitative analyses of the natural phytoplankton population was also carried out.O. edulis suffered catastrophic summer mortalities at all locations when the ambient temperature of the water reached about 25°C; this virtually rules out any possibility of starting any flat oyster industry using this system. As for C. gigas, Marsaxlokk bay 3 m appears to hold some promise for its culture. At this location, this species showed reasonable growth, relatively low mortality and normal shell growth. Although at Rinella overall growth of C. gigas was comparable to that at Marsaxlokk at 3 m, the Rinella oysters accumulated copper and exhibited abnormal and thickened shell growth with the result that the oysters were of a much inferior condition. Growth at Mistra (both depths) and Marsaxlokk 8 m was stunted.No clear correlation could be established between the performance of the oysters and the environmental parameters monitored. Several factors that may have been responsible for the observed differences in oyster performance are discussed. In particular, the nature of the water movements is thought to have played a key role in dictating the growth of the oysters.     

Species diversity of the marine diatom genus Skeletonema in Japanese brackish water areas

The genus Skeletonema includes phytoplankton species that are important primary producers in marine food chains. Brackish waters have been reported to be one of the important habitats of some species of Skeletonema. To elucidate the species diversity of Skeletonema in brackish waters, we investigated three Japanese brackish bodies of water: the coastal waters of Toyama Bay, a tidal area of the Chikugo River, and a constructed reservoir in Isahaya Bay. We used molecular analysis based on large subunit rDNA and fine morphological structure to identify species. Skeletonema costatum s.s. (sensu stricto) was isolated at salinities as low as 0.6, but Skeletonema dohrnii, Skeletonema subsalsum, and Skeletonema tropicum were not found at salinities below 11.0. S. costatum s.s. could survive transfer from a medium with a salinity of 15 to a salinity of 2, but S. dohrnii did not survive in the same experiment. Only S. costatum s.s. germinated from the sediment of a reservoir in which the salinity was 0.1–1.4; incubation conditions included temperatures of 10, 15, 20, 25, and 30 °C and salinities of 5 and 30. Skeletonema costatum s.s. was identified as the species most adaptable to low-level salinity variations throughout its lifecycle.     

Effects of immersion salinity on the food properties of shucked oysters

The effects of immersion salinity on the food properties [water content, salinity, and free amino acid (FAA) content] of shucked oysters were analyzed. Results of a laboratory immersion experiment suggested that the molluscous parts (other than the adductor muscle) swelled in lower salinity and shrank in higher salinity. Higher FAA content was observed in oysters immersed in higher-salinity water. In the adductor muscle, water content increased and FAA content decreased markedly following immersion, regardless of salinity, probably because of intake of immersion fluid and leakage of FAAs across the cut end of the adductor muscle. Immersion salinity ranged from 0.17 to 1.54 % in shucked oyster products on the retail market. Tissue salinity was strongly correlated with immersion salinity (r = 0.904), and tissue water content was correlated negatively with immersion salinity (r = ?0.668). In addition, total FAA and taurine content of oysters were correlated with immersion salinity (r = 0.629 and 0.865, respectively). These results clearly indicate that immersion salinity is an important factor affecting the food components of shucked oysters.     

Effect of body size and sub-optimal water quality on some hemato-immunological parameters of spotted babylon snail <Emphasis Type="Italic">Babylonia areolata</Emphasis>

Cellular and humoral effectors are imperative for the innate defense mechanisms of invertebrates, including the spotted babylon snail Babylonia areolata, a marine gastropod belonging to the family Buccinidae. In this study, we have investigated the influence of body size [5–8 g (small), 10–12 g (medium) and 15–17 g (large)], and culture waters of varied quality [natural seawater, low salinity, low alkalinity, high total ammonia nitrogen (TAN) and artificial seawater] on some hemato-immunological parameters [total hemocytic counts (THC), hemolymphatic glucose, total protein concentration, phenoloxidase (PO), agglutinating and lysozyme activity] of the snail. Growth performance measures and survival of test snails were also evaluated after rearing them in culture water of varied quality. Body size did not influence most parameters assessed, except that the lysozyme and PO activities of medium and large-size snails were higher than those of the small-size snails. Sub-optimal culture water quality affected hemato-immunological factors, growth and/or survival of the spotted babylon snail. Seawater with low salinity, low alkalinity and a high TAN level caused decreased THC, hemolymphatic glucose, and PO activity; increased lysozyme activity; and clearly retarded growth of the snail. The snails held in artificial seawater could not survive after 4 weeks, suggesting the lack of certain essential factors necessary for their survival.     

Effects of salinity on the ions important and sodium‐potassium ATPase in osmoregulation,cortisol, amino acids,digestive and immune enzymes in Scylla paramamosain during indoor overwintering

Overwintering is an important part of the conservation of Scylla paramamosain, and salinity has an important effect on the conservation of S. paramamosain during overwintering. Three salinities (4‰, 12‰ and 25‰) were selected as the overwintering salinities to reveal the effects of different salinities on the relevant important ions in osmotic pressure regulation, plasma cortisol, digestive enzymes, immune enzymes and amino acids of S. paramamosain during indoor overwintering. Results indicated that after overwintering, Cl^‐, Na⁺ and the osmotic pressure of serum have the highest salinity at 25‰, and the lowest salinity at 4‰. Na⁺/K⁺‐ATPase activity and cortisol were found to increase with decreasing salinity. The activity of digestive and immune enzymes was highest at 25‰, and was the lowest at 4‰. The amount of total amino acids (TAA), umami amino acids (UAA) and essential amino acids (EAA) in 25‰ were significantly higher than in 4‰ and 12‰. After overwintering, the essential amino acid index (EAAI) in the salinity range of 12–25‰ was 54.04–59.00, compared to 48.56–54.04 in the salinity range of 4–12‰. As a result, S. paramamosain at 25‰ had higher digestion and immunity than at 4‰ and 12‰, due to requiring more energy for osmotic pressure adjustment. In addition, S. paramamosain at 25‰ had the best meat quality. The results of this study are helpful for aquaculture production for indoor overwintering of S. paramamosain.     

Physiological short-term response to sudden salinity change in the Senegalese sole (Solea senegalensis)

The physiological responses of Senegalese sole to a sudden salinity change were investigated. The fish were first acclimated to an initial salinity of 37.5?ppt for 4?h. Then, one group was subjected to increased salinity (55?ppt) while another group was subjected to decreased salinity (5?ppt). The third group (control group) remained at 37.5?ppt. We measured the oxygen consumption rate, osmoregulatory (plasma osmolality, gill and kidney Na⁺,K⁺-ATPase activities) and stress (plasma cortisol and metabolites) parameters 0.5 and 3?h after transfer. Oxygen consumption at both salinities was higher than for the control at both sampling times. Gill Na⁺,K⁺-ATPase activity was significantly higher for the 55?ppt salinity at 0.5?h. Plasma osmolality decreased in the fish exposed to 5?ppt at the two sampling times but no changes were detected for high salinities. Plasma cortisol levels significantly increased at both salinities, although these values declined in the low-salinity group 3?h after transfer. Plasma glucose at 5?ppt salinity did not vary significantly at 0.5?h but decreased at 3?h, while lactate increased for both treatments at the first sampling time and returned to the control levels at 3?h. Overall, the physiological response of S. senegalensis was immediate and involved a rise in oxygen consumption and plasma cortisol values as well as greater metabolite mobilization at both salinities.     

Evaluation of progeny of fourth generation Sydney rock oyster Saccostrea glomerata (Gould, 1850) breeding lines

The progeny of four 4th generation Sydney rock oyster Saccostrea glomerata (Gould, 1850) breeding lines that were selected for fast growth were compared in a 3‐year farming experiment. Oysters of the most improved breeding line (line 2) reached market size (≥50‐g whole weight) 15 months earlier than non‐selected control oysters (3 years and 5 months). The average reduction in time to market size for oysters of all four breeding lines was 12.5 months.     

Response of ATPases in the osmoregulatory tissues of freshwater fish Oreochromis niloticus exposed to copper in increased salinity

An increase in salinity of freshwater can affect the physiology and metal uptake in fish. In the present study, Nile tilapia Oreochromis niloticus were exposed to copper (1.0 mg/l) in increased salinities (2, 4, and 8 ppt) for 0, 1, 3, 7, and 14 days. Following the exposures, the activities of Na⁺/K⁺-ATPase, Mg²⁺-ATPase, and Ca²⁺-ATPase were measured in the gill, kidney, and intestine to evaluate the changes in osmoregulation of fish. Results showed that increases in salinity and Cu exposure of fish significantly altered the ATPase activities depending on the tissue type, salinity increase, and exposure durations. Salinity-alone exposures increased Na⁺/K⁺-ATPase activity and decreased Ca²⁺-ATPase activity. Na⁺/K⁺-ATPase activity decreased following Cu exposure in 2 and 4 ppt salinities, though the activity increased in 8 ppt salinity. Ca²⁺-ATPase activity decreased in the gill and intestine in all salinities, while the activity mostly increased in the kidney. However, there were great variations in Mg²⁺-ATPase activity following exposure to salinity alone and salinity+Cu combination. Cu accumulated in the gill and intestine following 14 days exposure and accumulation was negatively correlated with salinity increase. Data indicated that ATPases were highly sensitive to increases in salinity and Cu and might be a useful biomarker in ecotoxicological studies. However, data from salinity increased freshwaters should carefully be handled to see a clear picture on the effects of metals, as salinity affects both metal speciation and fish osmoregulation.     

盐度胁迫对尼罗罗非鱼免疫相关指标的影响

为探究盐度胁迫对尼罗罗非鱼免疫的影响,对体质量(35.0±5.0) g的尼罗罗非鱼进行了急性和慢性的盐度胁迫实验,对免疫相关指标进行了检测和分析。在急性盐度胁迫中,设置0、5和15盐度组,分别在胁迫后6、12、24、48和96 h进行取样,检测血清SOD、CAT、GSH-Px和AKP的活性。在慢性实验中,设置0、10、20和30盐度组,胁迫8周后检测血清SOD、CAT、GSH-Px和AKP活性,并进行了无乳链球菌易感性实验。结果显示：①血清中SOD活性在急性盐度胁迫6、12和24 h时都有随盐度上升而上升的趋势,但在96 h时盐度15组酶活性显著低于盐度5组;在慢性盐度胁迫下,各组的酶活性呈现出随着盐度升高而显著性下降的趋势。②血清CAT活性在急性盐度胁迫下12和24 h时呈现出随着盐度升高而显著下降的趋势;在慢性胁迫下不存在显著性差异。③血清中GSH-Px活性在急性和慢性胁迫后,均呈现随着盐度升高而降低的趋势。④血清AKP活性在胁迫后6 h随盐度升高呈现出显著下降趋势;在慢性盐度胁迫下,盐度20组显著低于其他实验组。⑤尼罗罗非鱼对无乳链球菌易感性实验中,盐度10组的易感性和盐度0组之间无显著差异,盐度20和30组的易感性高于盐度0组。研究表明,两种盐度胁迫均会引起免疫相关指标的变化,急性盐度胁迫实验表明,盐度5和15可导致尼罗罗非鱼机体氧化损伤,但尼罗罗非鱼可以逐渐适应这一变化;慢性盐度胁迫实验表明,盐度高于20会抑制尼罗罗非鱼多种免疫指标活性,造成其对无乳链球菌的易感性升高。     

Experimental feeding of Sydney rock oysters (Saccostrea commercialis). III. Food concentration and fattening procedures

Sydney rock oysters (Saccostrea commercialis) were fed an artificial diet at 0, 3, 6, 9, 12 and 15 mg dry food/l. At 9 mg/l oyster glycogen content, condition indices and meat weight gains were maximised without increasing mortality rates. In a comparison of fattening procedures, oysters held in a fertilised pond and those fed a second artificial diet fattened in 4 and 6 weeks respectively, whereas those held in an estuary did not fatten at all. The artificial diet produced higher oyster meat glycogen contents than the fertilised pond and estuary treatments.     

Combined effects of salinity and potassium concentration on juvenile mulloway (Argyrosomus japonicus, Temminck and Schlegel) in inland saline groundwater

This paper reports on experiments conducted to examine the combined effects of salinity and potassium concentration on survival and growth of juvenile mulloway (Argyrosomus japonicus, Temminck and Schlegel) in inland saline groundwater. Three separate experiments were conducted in 20 (±1)°C water. In the first experiment, mulloway were held in 60 L aquaria (triplicate) with salinities of 5, 15, 25 or 35 g L^?1 and potassium concentrations of 20%, 40%, 60% or 80% of the concentration present in oceanic water of the equivalent salinity in a 4 × 4 factorial combination for 7 days. Response surface contour diagrams were generated from survival data to estimate optimal conditions. The results showed that maximum survival of juvenile mulloway occurred at salinities of >14 g L^?1 and potassium concentrations of >38%. Survival was lowest at salinities of <7 and >33 g L^?1 and potassium concentrations of <25%. The second experiment was conducted with mulloway held in 60 L aquaria at salinities of 15, 25 or 35 g L^?1 and potassium concentrations of 40%, 60%, 80% or 100% in a 3 × 4 factorial combination for 44 days. Optimal conditions for maximum survival and growth of mulloway were within a salinity range of 15–35 g L^?1 and potassium concentration above 40%. The third experiment was conducted in three 500 L tanks to record the survival and growth of mulloway fingerlings held at 20 (±1)°C, 23 g L^?1 salinity and potassium concentrations of 50% for 8 months. Survival and growth of mulloway fingerling in inland saline groundwater were similar to those reported from a semi‐intensive floating tank system in inland saline water and sea cage trials in oceanic water.     

Evaluation of resistance to Dermo in eastern oyster strains tested in Chesapeake Bay

We investigated growth, Dermo disease, and survival for nine groups of oysters, Crassostrea virginica (Gmelin) cultivated in Chesapeake Bay (CB). Five regional strains (upper CB, North Carolina (NC), South Carolina (SC), Louisiana (LA) and LA triploids) and four additional hybrid strains (CB oysters mated with NC, SC, LA and Texas (TX) oysters) were held in floating rafts at three locations representative of lower CB: ‘low’ salinity (3–14 g L^?1), ‘moderate’ salinity (5–20 g L^?1) and ‘high’ salinity (14–24 g L^?1). At each site, patterns of growth and incidence of infection with Perkinsus marinus (Levine), the causative agent of Dermo disease, were similar. However, mortality trends were markedly different at each site; the CB strain being notable for accelerated mortality following infection with P. marinus. In addition, hybrids between CB and all four of the regional strains exhibited similar accelerated mortality in response to infection. Mortality was strongly correlated with infection only at the high salinity site implicating interaction of differences in both oyster strain and virulence of Dermo between moderate and high salinity areas as factors in differential mortality across sites.     

Rapid salinity changes affect the survival and physiology of a penaeid prawn: Implications of flood events on recruitment to the fishery

Estuaries act as nurseries for many penaeid prawns, but these habitats are highly susceptible to salinity decline through flooding. The rate of salinity decline and duration of exposure to non‐optimal salinity may affect survival and subsequent recruitment of prawns to the fishery. This study aimed to determine the effect of salinity fluctuations observed in local estuaries during flood events using a novel dilution approach. Mortality of juvenile Melicertus plebejus (Hess) was assessed after 24 hr exposure to 24 rates of salinity decline ranging from 0.01% to 20% per hr. After the salinity decline, prawns were held at the final salinities for five days before again assessing mortality as well as aerobic metabolic rate and prawn water content. Salinity decline from 36 to ~0.8 led to 50% mortality, but continued exposure to low salinity for five days increased mortality at this salinity to 99% and shifted the 50% mortality point to salinity ~5. Aerobic metabolic rate and water content data suggested the cause of mortality due to exposure to salinities < 5 was osmoregulatory failure. Rapid salinity declines over 24 hr and sustained low salinity due to flooding could compromise the survival of juvenile prawns, potentially reducing recruitment to the fishery.     

Shell shape and meat condition in selectively bred Sydney rock oysters,Saccostrea glomerata (Gould, 1850): The influence of grow‐out methods

The Australian edible oyster industry has been severely impacted by disease and declining yields since the 1970s. Selective breeding of Saccostrea glomerata is one measure addressing these problems by producing fast‐growing, disease‐resistant oysters. Farmers report that selected oysters have different growth characteristics than their wild counterparts using conventional grow‐out methods. This study investigated how different grow‐out methods influence commercially valuable oyster characteristics including shell length, shape, surface growth deformities and meat condition. In June 2015, selectively bred S. glomerata spat were deployed in two estuaries (Hawkesbury River and Georges River) in NSW, Australia, using three grow‐out methods (fixed trays, Stanway cylinders and floating baskets). In November 2015, oysters were transferred among grow‐out methods to test for the effects of changing grow‐out methods on oyster growth patterns. Oysters transferred from baskets to cylinders and from trays to cylinders had, on average, deeper and wider shells, a higher meat condition and fewer shell surface deformities than oysters in other grow‐out method combinations. However, these oysters were smaller than oysters not grown in cylinders. While there were some differences in growth patterns between the estuaries, overall it was the grow‐out methods that most influenced oyster characteristics. This was attributed to differences in the amount and magnitude of movement oysters experienced in the grow‐out methods, as recorded by motion sensors. This study demonstrates how grow‐out methods can be managed to achieve desired growth trajectories and therefore improve marketability among selective bred S. glomerata.     

The capacity of oysters to regulate energy metabolism‐related processes may be key to their resilience against ocean acidification

Bivalve molluscs, such as oysters, are threatened by shifts in seawater chemistry resulting from climate change. However, a few species and populations within a species stand out for their capacity to cope with the impacts of climate change‐associated stressors. Understanding the intracellular basis of such differential responses can contribute to the development of strategies to minimise the pervasive effects of a changing ocean on marine organisms. In this study, we explored the intracellular responses to ocean acidification in two genetically distinct populations of Sydney rock oysters (Saccostrea glomerata). Selectively bred and wild type oysters exhibited markedly different mitochondrial integrities (mitochondrial membrane potential) and levels of reactive oxygen species (ROS) in their hemocytes under CO₂ stress. Analysis of these cellular parameters after 4 and 15 days of exposure to elevated CO₂ indicated that the onset of intracellular responses occurred earlier in the selectively bred oysters when compared to the wild type population. This may be due to an inherent capacity for increased intracellular energy production or adaptive energy reallocation in the selectively bred population. The differences observed in mitochondrial integrity and in ROS formation between oyster breeding lines reveal candidate biological processes that may underlie resilience or susceptibility to ocean acidification. Such processes can be targeted in breeding programs aiming to mitigate the impacts of climate change on threatened species.